In recent years, use of an organic semiconductor material has been considered for semiconductor devices, such as transistors, diodes, and thyristors, which conventionally use inorganic semiconductor materials, such as silicon and gallium arsenide. Most of the organic semiconductor materials are capable of evaporating in a relatively low temperature, such as 100 degree/C. to 200 degree/C. Also, by dissolving into a solution, a semiconductor layer may be formed by a printing method, such as ink-jet. Therefore, significant cost reduction may be realized by fabricating a semiconductor device using the organic semiconductor material, compared to a case where the inorganic semiconductor material is used to fabricate.
Japanese published unexamined patent application No. 2006-37098 proposes, as a semiconductor material, an organic semiconductor polymer, which simultaneously shows p-type and n-type electric characteristics by alternately containing an oligothiophene that has the p-type semiconductor characteristic, and an aromatic heterocyclic ring that has the n-type semiconductor characteristic in a polymer main chain.
Japanese published unexamined patent application No. 2006-117672 proposes an oligothiophene-allylene derivative that introduces an allylene having a n-type semiconductor characteristic to an oligothiophene unit having a p-type semiconductor characteristic.
However, the carrier mobility of such a conventional organic semiconductor material is not sufficient, and there has been a demand for new organic semiconductor materials with higher carrier mobility. Further, the on/off ratio, which is a ratio of the current in an on-state and the current is an off-state, is not sufficient when used as an organic transistor, therefore, there has been a demand for a new organic semiconductor material which demonstrates a higher on/off ratio.
Further, there has been a demand for an organic semiconductor material capable of easily controlling a threshold voltage Vth, which is a voltage that transits the on-state and the off-state, to a predetermined voltage in a case when used as an organic field effect transistor.
Further, there has been a demand for an organic semiconductor material capable of dissolving in an inexpensive organic solvent with an adequate volatility in a case when forming a semiconductor layer by the printing method such as ink-jet.